Normal dresser for grinding wheels



15, 1942. A. LI'URNER 2,304,970

NORMAL DRESSER FOH GRINDING WHEELS Filed May 22, 1941 Patented Dec. 15, 1942 l UNITED STATES PATENT OFFICE 21,304,970 i NORMAL DRESSER FOR GRINDING WHEELS Albert Turner, Springfield, Vt., assignor to, The Fellows Gear Shaper Company, Springfield, Vt., a corporation of Vermont 7 Application May, 22, 1941, Serial No. 394,651

' 12 Claims. (01.125-11) The object of this invention is to provide a dressing or truing appliance for grinding wheels and the like adapted to generate surfaces of revolution of which the elements in planes radial to the wheel are otherwise than straight, and to maintain the axis of the dressing point normal, or approximately so, to the surface at all times in the course of its traverse over such surface. In this specification the word norma is used with a meaning analogous to that ascribed to it ingeometry, and denotes the position of a straight line drawn at right angles to the tangent line of a curve, or to a plane. As applied to a dressing tool of tapered or rounded formation at the extremity which makes contact with the grinding wheel, it means that the axis of the taper, or the central radius of the protuberant terminal curve, is substantially perpendicular to the elements of the dressed face of the grinding wheel in radial planes of the wheel. Where the dressing tool has a short straight edge, which may be used on plane and convex grinding faces, the line to be maintained normal to the grinding wheel face is a line substantially perpendicular to such straight edge located between its limits, whereby the truingedge is maintained tangent to the curve.

Many occasions arise where a grinding wheel must be formed with a curve or angle of revolution in its active face in order to produce a complemental or conjugate curve in the work piece being ground. One such use is found in the grinding of gear teeth and the teeth of gear shaper cutters, wherein an involute curve is generated by rolling contact between the work piece and a plane surface on a grinding wheel, and a portion of the tooth face is to be modified from the true involute curve either by leaving excess stock on, or removing additional stock from such portion. In such case the part of the wheel face which generates the modified curve in the work is,

wheels, the provisions for maintaining the truing tool in normal relation to the face being dressed have been limited tosituations where the path of the truing tool is a straight line, or a simple curve, such as the arc of acircle or other curve having the same character throughout. Where wheels were made'with profiles composed of lines and curves of difierent characteristics or, in terms of analytical geometry, having different equations, it has been necessary to make special adjustments or substitutions of different truing devices in order to maintain the tool in the normal relation to such different parts of the grinding wheel.

- The object of this invention is to cause a truing tool; when traversing the face of such a wheel, to change its angularity upon arrival at the junction point between two such lines, and maintain it in normal relation to the line traversed after passing the junction point, whether such line is straight or curved. It is part of this object to insure that the junction between the lines of different characteristics is correctly established, and to do so without making special adjustments of the apparatus or even arresting the progress of the truing tool. One of the embodiments of means for accomplishing this object, to illustrate theprinciple of the invention is described in the following specification with reference to the accompanying drawing, but without intent to limit my protection to such embodiment.

In the drawing:

Fig. 1 is a plan view of a dressing tool shown in one stage of its use for generating a plane surface in the marginal part of a circular grinding Wheel and a curve at the rim of the wheel i Fig. 2 is a similar view of the tool at another stage of its operation;

Fig. 3 is a cross section on line 3-3 ofFig. 1;

Figs. 4 and 5 are partial cross sections of the truing device taken on lines 4-4 and 5-5, respectively, of Fig. 1;

Fig. 6 is a diagram illustrating the operation of the means here illustrated for maintaining the dressing tool normal to the face of the grinding wheel; I

Fig, 7 is a fragmentary radial section of the rim portion of the grinding wheel on a larger scale than that of Figs. *1 and 2.

Like reference characters designate the same parts wherever they occur in all the figures.

. The grinding wheel G, of which a fragment is shown in Figs. 1, 2, 3 and 7, is a dished circular disk having a grinding face in its marginal portion. The major part of the face 1 lies in a plane perpendicular to the axis of revolution of the wheel, while the part ,f at the rim of the wheel is a curved surface of revolution of which the curvature in planes radial to the wheel axis is the arc of a circle centered at ,P. The dressing apparatus comprises a base It adapted to be mounted on any convenient part of the frame of a grinding machine, or the grinding wheel carriage of such a machine, or on a special dressing machine to which grinding wheels may be brought when in need of dressing. The base In supports tracks I I, I2 and I3, on which a carriage I4 is mounted by means of rolls I5, I5, I! and I8. A dressing tool, consisting of a'screw threaded bar or shank I9 having a diamond 22 or other suitable hard element in its extremity (all elements suitable for the purpose being comprehensively included within the term diamond as used herein), is mounted in the carriage with said extremity protruding therefrom 7 toward the grinding wheel. This dressing tool is adjustable inand out by rotation in a complementally screw threaded longitudinally split bushing 20, which is set into the carriage and is secured, and clamped on the dressing tool by a set screw 2|.

The active point or edge of the diamond 22 is located in, and in symmetrical relation with, the longitudinal center line of the bar I9. Such line is considered to be the axis of the dressing tool. For generic definition, the axis of the dressing tool is a line passing through the active point, or that point of the cutting edge which is designed to be tangent to the grinding wheel, in the action of truing, symmetrical to the surfaces adjacent to the point and normal to the cutting edge. The axes of the rolls I and I6 (in the present illustration) are in the same plane with the axis of the dressing tool, and the projections of the centers of the rolls and of the dressing tool axis, in the plane in which the point travels, are all in the same straight line. the line 33 in Fig. 1 and is shown at PQ in Fig. 2. This location of roll I5, however, is not essential, provided the dressing point and roll I6 are maintained in a line normal to the wheel surface. s

The plane in which the path of the dressing point lies is determined by the locations of the tracks II and I2. For dressing the particular wheel here shown, tracks are provided which have straight and curved portions. The straight portions are designated I Ia and I2a, and the curved portions are IIb and I2b. The curves IIb and I2b are concentric with the center P and their junctions with the straight portions I la and I2a are in a straight line P-R radial to this center. Although both tracks are shown as in the same plane, they may be in different but parallel planes. 7

The chief problem solved by the invention wa to maintain the dressing tool axis P-Q normal to each of the straight and curved portions of the track and to change its angularity with respect to the straight portions Hat and IZa at the instant of crossing the junction points between such straight portions and the curved portions I ID and I2b. Thi problem was solved by providing an auxiliary track I3 and pilot rolls I! and I3 to cooperate with such track and the V curved track section I2b. The rolls I1 and I8,

I2a and is located in the same plane with. the 15.

This line coincides with path of roll II. Its location with respect to the straight track sections Na and I211 correspond to the location of roll I! on the carriage with re spect to rolls I5 and I6. Thus when the rolls I5 and I6 travel along the straight track sections, roll I7 travels along track I 3, maintaining the dressing tool axis normal to a straight line; and when the rolls I5 and I6 cross the junction points in passing to the curved track sections, roll I? reaches the point wher the tracks I3 and I2?) cross, and roll I8 then engages the track section I21) and controls the angularity of the dressing tool axis.

The effects just described are illustrated graphically in Fig. 6. Here the carriage is represented diagrammatically in thre different stages of travel in the direction of the arrow A. In the first position the rolls I5, I6 and I! are shown as traversing intermediate portions of the track sections I la, I2a and I3 respectively, In the second position the rolls I5 and It, here designated as I5a and led, have reached the junctions with the curved track sections and the roll II has come to the position Ila where the roll I8 engages the track section I21). In the third position the roll II has left track I3, roll I8, here designated as I8b, has traveled along the track section 12b and the rolls I5 and I6 have reached the positions I5?) and IIib. In the course of these movements of the carriage th truing point 22 has passed first in a straight line to the point 22a and then in the arc of a circle around center P to the position 221).

Means are provided to take up looseness and wear between the rolls I5 and I6 and the tracks II and I2, and to press rolls I1 and I8 against their cooperating track sections. Preferably the tracks are made with beveled or V edges and the rolls are of complemental recessed conical form; the tracks being supported on the base Ill by any suitable structure or means. The roll I5 is made of separable parts, of which one part is secured to its shaft 24, and the other part is pressed toward the adjacent beveled face of the track by a spring 25. A nut 26, threaded on shaft 24, serves as the adjusting means. Thus by the Wedging action of these parts roll I6 is forced firmly against track I 2, which is the master guide.

To maintain the rolls I7 and I8 firmly against the cooperating track sections I3 and IZb, a dog or pusher 21 is mounted rotatably on the carriage and pressed by a powerful spring 23 against an abutment 29 which has a bearing surface 35 following an outline similar to th projection of the track I3 and track section I212. The dog 21 and spring 28 are fastened to opposite ends of a shaft 3I, located in the carriage near the rolls I! and I8; the spring is anchored to the carriage by a pin 32, and the extremity of the dog is at one side of th shaft axis; the arrangement of spring,

dog and abutment being such as to exert pressure of the roll I8 against track section I22) and of roll I'I against track section I3. It is desirable to maintain a substantially uniform pressure of the pilot rolls against the tracks, and for that purpose the abutment surface 39 has straight and surved portions arranged to be engaged by the dog when the pilot rolls engage the straight track I3 and the curved track section I21), respectively. The carriage may be propelled along the tracks either manually or by automatic -means.- The means here shown for illustration consists of a hand crank 33 on a shaft 34 mounted in the carriage, to'which is secured a gear 35 meshing with rack teeth 36 on the outer side of the track [2.

The relation of the path traversed by the truing point to the center P may be varied by in and out adjustment of the tool shank l9; and the relation of the center to the wheel being trued may be varied by adjusting the dressing apparatus as a whole toward and away from the wheel or, conversely, adjusting the wheel with respect to the truing apparatus. Clamp screws 31 passing through slots in the base I!) into a supporting structure are here shown as illustrations of any suitable provisions for effecting such relative adjustment. By combinations of these adjustments, curves of any desired radius, within limits, tangent to a plane, may be formed in the grinding wheel face.

It will be evident that many variations may be made in details without departing from the spirit and scope of the invention. For instance, I am not limited to operating the dressing point in paths consisting of a straight section and a circular arc. These principles are readily adaptable without independent invention for causing the dressing tool to travel in angularly related straight lines, in curves of other character than circular arcs, and in paths containing various sequences of straight and curved sections; all by providing appropriate tracks generally similar to the desired profile of the grinding face.

It will be clearly apparent also that the track l3 could be extended by a curve parallel to the track section [2b for continuous engagement with the roll I! throughout the travel of the carriage. In other words, it is not essential that the pilot coact during a part of its travel, or at any time with the main track. In the present embodiment it was more convenient to provide a double pilot roll and shorten the track l3. But other circumstances readily suggest themselves where a single continuous track for the pilot is preferable. In any embodiment of the invention the pilot performs the vital function ofcontrolling the angularity of the dressing tool axis so that it is kept substantially normal to the angularly related zones of the wheel being trued; and a track of suitable outline is provided for guiding the pilot. The lines of the track for any specific case are readily determined from the prescribed grinding face profile by the principles of descriptive geometry. The track II and roll l5 are a convenient means for assisting in the support of the carriage and in holding guide roll l6 firmly against the control track l2. Either or both may be positioned otherwise than as shown, and equivalent other means may be substituted. However, I prefer these specific parts, in the arrangement shown, to other means because of their efiiciency and simplicity.

What I claim and desire to secure by Letters Patent is:

1. An apparatus for generating on a grinding wheel or the like a surface of which the profile in planes radial to the wheel is composed of lines of respectively difierent characteristics inclined one to another, comprising a support having guide means extending in paths similar to said lines in a given plane of the wheel, a carriage mounted to travel on said guide means progressively from one of said paths to the next adjoining path, a dressing tool mounted on the carriage for engagement with the face of the wheel to be dressed, and means cooperating between the carriage and guide means for changing the inclination of the dressing tool axis when the carriage'passes from one part of the guide means to another part which lies at an inclination to the first mentioned part.

2. A wheel dressing apparatus comprising a base, guide means supported by the base having guide elements spaced apart from each other and extending in similar courses, parts of which are inclined to other parts, a carriage having guide engaging members adapted to engage said guiding elements simultaneously, in any parts thereof, when disposed in lines normal to such parts, a dressing tool mounted on the carriage with its axis in or parallel to the straight line joining the engaging parts of said elements, and pilot means on the carriage at one side of the line through said engaging members normal to said guide elements arranged to maintain the line between said engaging points normal to the guide elements in all positions of the carriage thereon.

3. A wheel dressing apparatus comprising a base, tracks on the base spaced apart from each other in substantially the same plane, each having sections inclined to one another, the courses established by such sections of one track being similar to those of the other, a carriage having track engaging members spaced apart from each other by distances equal to the distance between corresponding portions of the two tracks in lines normal to the latter, a dressing tool mounted on the carriage with its axis substantially in or parallel to the straight line between said engaging points, a pilot mounted on the carriage at one side of the line connecting said engaging points, and means on the base cooperating with the pilot for effecting a change in the inclination of said line of contact points when passing from one section of the tracks to another section inclined thereto.

4. A wheel dressing device comprising a carriage having spaced apart track engaging members, a dressing tool mounted on the carriage with its axis substantially coincident with or parallel to the straight line between said members, a pilot mounted on the carriage at one side of said line, a supporting structure, tracks on the supporting structure extending in similar spaced apart courses composed of sections inclined to one another, and a track element arranged to engage said pilot for guiding the same to maintain the line of said engaging members normal to the tracks when said members pass from one section to a relatively inclined section of the tracks.

5. An apparatus for dressing grinding wheels to a profile of which part is a straight line and a contiguous part is a curved line, comprising a supporting structure, two tracks each having a straight portion and a curved position similar to the curvature to be generated in the dressed wheel, said tracks being spaced apart from each other substantially in the same plane and at equal distances apart in all lines normal to them, a carriagehaving track engaging members spaced apart a distance equal to-the normal distance between the tracks, in engagement with the respective tracks, a pilot mounted on the carriage at one side of the line joining said engaging members, another track extending parallel to the straight portions of the before named tracks located to guide said pilot and maintain the line of the engaging members normal to said straight portions when the engaging members occupy such straight portions, and a dressing tool mounted on the carriage.

6. A dressing apparatus .as set forth in claim 5, combined with an abutment having a contact surface similar to the courses of the track means by which the pilot is guided, and resilient means acting and reacting between the carriage and said abutment organized to hold the pilot in contact with its guiding means.

7. A Wheel dressing apparatus comprising a base tracks mounted on the base side by side having straight and curved portions similar to each other and spaced equal distances apart in all. lines normal to corresponding parts of the two tracks, a carriage, track engaging rolls mounted on the carriage with a spacing between them such that they engage the tracks simultaneously, each engaging one track, when the straight line between them is normal to the tracks, a dressing tool mounted on the carriage, a pilot roll also mounted on the carriage at one side of the line joining the first named rolls, said roll being located to engage the curved portion of one of said tracks when the first named rolls engage the curved portions of the two tracks and the line between said rolls is normal to said curved portions, and a straight track parallel to the straight portions of the before named tracks located to engage and guide the pilot roll when the first named rolls engage the straight portions of the first named tracks and the line between said rolls is normal to said straight portions.

8. A dressing apparatus for forming the face of a grinding wheel with a plane portion and a contiguous curved portion inclined to said plane portion, comprising a carriage, a dressing tool protruding from said carriage having a dressing point, a base having guide means on which said carriage is mounted to travel, said guide means having straight and curved portions similar to the different parts of the prescribed profile of said grinding face, and means on the carriage and base, respectively, cooperatively interen- 'gaged to cause angular swing of the carriage at the junction between said portions in traversing said guide means whereby to maintain the axis of the dressing tool normal to the prescribed grinding face profile while traversing such profile.

9. A dressing apparatus for generating on a grinding wheel or the like a surface of which the profile is composed of lines having respectively different characteristics in junction with one another, comprising a carriage, a dressing tool mounted on the carriage and guiding means associated with the carriage constructed to constrain and permit continuing movement of the carriage such that the dressing tool may traverse said lines in succession, and including means for maintaining the axis of the dressing tool normal to each said line of the wheel profile in turn and for effecting angular shift from normality with the preceding line to normality with the subsequent line when said axis arrives at the junction between said lines in the course of progressive movement of the carriage.

10. An apparatus for the purpose set forth, comprising a carriage, guide means with which the carriage is cooperatively engaged with provision for movement'in a prescribed path, and a dressing tool mounted on the carriage, said guide means including successive portions angularly related in the manner of adjoining lines of respectively difierent characteristics, the dressing tool being so mounted that its axis is normal to one of said lines when the carriage is engaged with the portion of the guide means corresponding to such line, and associated cooperative means organized to shift the carriage angularly when, in the course of its continuing travel, the dressing tool axis crosses the junction point between such line and the adjoining line of different characteristics.

11. A grinding wheel dressing apparatus comprising a track composed of a straight portion and a curved portion each in continuation of the other, a carriage engaged with said track and being movable thereover, a pilot on the carriage, cooperating guide means in fixed relation to said track and in engagement with the pilot, said pilot, engaging means and dressing tool being interrelated to cause the dressing tool axis to be and remain normal to the track at all points in which it is located by travel of the carriage.

12. An apparatus for dressing a grinding wheel of which the profile is composed of lines having respectively diiferent equations, comprising {a supporting structure having tracks extending side by side with equal normal spacing between them and arranged in lines similar to the different lines of the grinding wheel profile, a carriage, a dressing tool mounted on the carriage, guide rolls on the carriage engaged with said tracks at points substantially in line with the axis of the truing tool, a pilot on the carriage at one side of said line, and means on the supporting structure in cooperative engagement with said pilot to hold the before mentioned line normal to the portion of the tracks with which said rolls engage, and to shift the carriage angularly when passing from one portion of the tracks to a difierent portion thereof, in the direction and to the extent that such line becomes normal to such different portion.

ALBERT TURNER. 

